Numerical investigation of the aerodynamic benefits of wing-wing interactions in a dragonfly-like flapping wing

Abstract

Numerical simulations are performed to investigate the aerodynamic benefits of wing-wing interactions on a dragonfly-like flapping wing while hovering, at a value of Reynolds number Re set to 630. The local phase shift ψ and wing spacing L* (L/c) are varied to observe their influence on aerodynamic performance. The results show that the aerodynamic benefits due to interactions are strongly dependent on both ψ and L*. The wing-wing interactions are beneficial for the in-phase stroking pattern at ψ = 0° when 1.2 ≤ L* ≤ 2.3, while it is extremely detrimental for the counter stroking pattern at ψ = 180° when 1.2 ≤ L* ≤ 2.3; these benefits and drawbacks are dependent on the timing of the interactions. The best case, when ψ = 0° and L* = 2.1, can increase the time-averaged vertical force coefficient \(\overline{C_v}\) up to ∼10 % in comparison to the without-interaction case. Two unsteady flow features namely the “enhanced dipole structure” and the “in-sync of wake capture and wing-wing interactions” are observed that increase the vertical force generation in hovering dragonflies. The overall downward momentum imparted by the wing is larger for ψ = 0° in comparison to ψ = 180° as the wake has high vertical velocities due to the constructive role played by wing-wing interactions.

Keywords

Dragonflies Flapping wing Insect flight Tandem Wing-wing interactions

Recommended by Associate Editor Donghyun You

Arun Raj Shanmugam has received M.Tech. (Eng) from IIT Bombay in 2012. He is currently pursuing Ph.D. at School of Mechanical Engineering, Kyungpook National University, Daegu. His research interests include turbo machines, CFD and fluid-structure interaction.

Chang Hyun Sohn has received M.Sc. (Eng) from KAIST in 1985. He then received his Ph.D. from KAIST in 1991. He worked in ADD for 3 years. He also worked in Cambridge University as a Visiting Assistant Professor from 1996 to 1997. Dr. Sohn is currently a Professor at School of Mechanical Engineering, Kyungpook National University, Daegu. His research interests include CFD, PIV, flow induced vibration, thermal-hydraulics and fluid-structure interaction.